The fourth Lockheed Martin F-22 Raptor, aircraft 4004. Is due to make its first flight from Marietta. GA, in late July. As the first F-22 to carry offensive avionics. Its task is to demonstrate that a stealthy aircraft can be a fighter. Under a deal struck with Congress last year, the F-22 has to prove this key technology by the end of this year if the next ten aircraft are to be authorized.

The F-22 represents a radical departure from the traditional approach to EW. Passive systems, once considered to be defensive in nature, are now critical to detecting, tracking and even attacking the target. The active radar, while still a primary sensor, is used sparingly for specific tasks. Active jamming in the traditional sense has disappeared. The F-22 approach is echoed to some extent in most of today's advanced fighter programs, including the Dassault Rafale, Eurofighter typhoon and Saab JAS Gripen. It is also fundamental to the future of the Joint Strike Fighter (JSF).

The F-22's EW philosophy is rooted in some of the earliest work on stealth. As the US Air Force (USAF) defined requirements and operational doctrine for the F-117 stealth strike aircraft and B-2 bomber, in 1980-81, A "Red Team" headed by Dr. Paul Kaminski was charged with looking for weaknesses and vulnerabilities in stealth technology. One of the Red Team's Most important conclusions was that a stealth aircraft could not survive by low radar cross-section (RCS) alone, but by stealth and tactics.

In the case of the F-117 the Red Team's recommendation resulted in the development of one of the first automated mission-planning systems, but this left the aircraft dependent on a pre-programmed flight plan. The B-2 was designed to feature a sophisticated defensive management system (DMS) which would allow the crew to respond to threat radars not anticipated by the mission plan. The initial DMS was abandoned in the late 1980s. Its successor is the APR-50, developed by IBM Federal Systems (later acquired by Loral and now part of Lockheed Martin). The USAF's Advanced Tactical Fighter project, which led to the F-22, presented greater challenges. In the air-to-air regime, the primary threats are airborne and move rapidly, making identification, location and tracking more complex. The F-22's sustained speed also shortens engagement timelines by as much as 40 percent. At the same time, the fighter's classic tool for situational awareness -- a powerful search radar -- can render its stealth characteristics moot. Low-probability-of-intercept (LPI) techniques are not very compatible with continuous searches over a large volume. The fighter's stealth is also of little use if it has to close to visual range in order to identify its targets. Passive search and track and non-cooperative target recognition (NCTR) are not luxuries for a stealthy air-superiority fighter. The solution to this problem on the F-22 is sensor fusion. The principal sensors are the Northrop Grumman APG-77 radar and the Sanders ALR-94 passive receiver system. The fighter also has two datalink systems: one using the standard VHF/UHF radio frequencies and the other, the intraflight datalink (IFDL), a low-power LPI link which connects two or more F-22s at close range. The sensors are apertures connected to the fighter's Common Integrated Processor (CIP) banks in the forward fuselage.

The data from the APG-77, ALR-94 and the datalinks are correlated according to their azimuth, elevation and range. Data is combined into a track file, and the final target picture is obtained by choosing the read-out from the most accurate sensor. For example, the passive system may provide the best azimuth data, while the radar produces the most accurate range.

CIP software controls the APG-77 according to emission-control principles. The radar's signals are managed in intensity, duration and space to maintain the pilot's situational awareness while minimizing the chance that its signals will be intercepted. More distant targets get less radar attention; as they get closer to the F-22, they will be identified and prioritized; and when they are close enough to be engaged or avoided, they are continuously tracked.

Sensor fusion and emission control are closely linked. The more the datalinks and ALR-94 can be used to build and update the tactical picture, the less the system needs to use the radar. The IFDL provides another layer of protection against tracking, because any one F-22 in a flight can provide radar data to the others. The APG-77 and ALR-94 are unique, high-performance sensors. The APG-77 has an active, electronically scanned array (AESA) comprising some 1,200 transmitter and receiver modules. One vital difference between an AESA and any other radar that has a single transmitter (including a passive electronically steered array) is that the AESA is capable of operating as several separate radars simultaneously. An AESA can change its beamform very readily, and its receiver segments can operate in a passive or receive-only mode. Unlike a mechanical antenna, too, its revisit rates are not constrained by the antenna drive, and it can concurrently revisit different points within its field of regard at different rates. The F-22 has space, weight and cooling provision for auxiliary side arrays on either side of the nose. If installed, these would provide radar coverage over almost 270[degrees]. The ALR-94, meanwhile, is the most effective passive system ever installed on a fighter. Tom Burbage, former head of the F-22 program at Lockheed Martin, has described it as "the most technically complex piece of equipment on the aircraft."

The F-22 has been described as an antenna farm. Indeed, it would resemble a signals-intelligence (SIGINT) platform were it not for the fact that the 30-plus antennas are all smoothly blended into the wings and fuselage. The ALR-94 provides 360[degrees] coverage in all bands, with both azimuth and elevation coverage in the forward sector.

A target which is using radar to search for the F-22 or other friendly aircraft can be detected, tracked and identified by the ALR-94 long before its radar can see anything, at ranges of 250 nm or more. As the range closes, but still above 100 nm, the APG-77 can be cued by the ALR-94 to search for other aircraft in the hostile flight. The system uses techniques such as cued tracking: since the track file, updated by the ALR-94, can tell the radar where to look, it can detect and track the target with a very narrow beam, measuring as little as 2[degrees] by 2[degrees] in azimuth and elevation. One engineer calls it "a laser beam, not a searchlight. We want to use our resources on the high-value targets. We don't track targets that are too far away to be a threat."

The system also automatically increases revisit rates according to the threat posed by the targets. Another technique is "closed-loop tracking," in which the radar constantly adjusts the power and number of pulses to retain a lock on its target while using the smallest possible amount of energy.

High-priority emitters -- such as fighter aircraft at close range -- can be tracked in real time by the ALR-94. In this mode, called narrowband interleaved search and track (NBILST), the radar is used only to provide precise range and velocity data to set up a missile attack. If a hostile aircraft is injudicious in its use of radar, the ALR-94 may provide nearly all the information necessary to launch an AIM-120 AMRAAM air-to-air missile (AAM) and guide it to impact, making it virtually an anti-radiation AAM.

Of course, there are some targets that do not emit signals. "We prefer it that way, because he's dumb," remarked one Boeing engineer. In this case, the F-22 can use its LPI features to track the target -- which is not a threat unless another radar is tracking the F-22 and datalinking information to the "quiet" aircraft -- and can, if necessary, identify it.

NCTR is a highly classified area. One of the few known techniques is jet-engine modulation, which involves analyzing the raw radar return for the characteristic beat produced by a combination of the radar-pulse frequency and the rotating blades of the engine. This technique is already used on operational radars (including the APG-70 in the F-15) but is vulnerable to countermeasures and dependent on target aspect.

Other NCTR techniques involve very precise range measurements. If the target's orientation is known, the distribution of the signature over very small range bins can yield a range profile which is characteristic of a certain aircraft type. It is possible that the F-22, which has a great deal of onboard processing power -- as well as a flexible, frequency-agile radar -- is designed to use an NCTR technique of this kind.

Unlike the Eurofighter Typhoon , the F-22 does not have an electro-optical (EO) system for target identification. F-22 program managers have said consistently that they believe that the F-22 pilot will be able to identify any target -- emitting or not -- beyond visual range (BVR). "We are confident that we can demonstrate to our leadership that we know what's out there, and that we will operate with rules of engagement that reflect that fact," USAF program manager Gen Mike Mushala remarked at a conference in 1997.

The ALR-94 drives the F-22's defensive displays. The system determines the bearing, range and type of the threat, and then computes the distance at which the enemy radar can detect the F-22. The pilot is the decision-maker and is provided with timely, graphic information to guide defensive maneuvers. On the main defense display, usually shown on the left-hand screen in the cockpit, threat surface-to-air missile (SAM) and airborne early warning (AEW) radars are surrounded by circles that show their computed effective range. On the right-hand attack display, fighter radars are shown as blue beams extending towards the F-22's position.

The F-22 has no dedicated jamming systems. However, the APG-77 array can be used to generate powerful jamming beams over a certain frequency range. Developing such a system has been a tremendous challenge. The F-22 avionics-development program is methodical and has learned from the experiences of other projects. From the outset, all of the software was designed on the same hardware with the same compilers and operating systems. "It was a tremendous advance," comments Boeing F-22 avionics deputy manager Gherry Bender. "We got beyond the hardware integration problems."

The complete system is being tested in three stages, starting with the ground-based avionics integration laboratory (AIL), then moving to the Boeing 757 flying test bed (FTB) and completing its tests on the F-22 prototypes. The AIL, located at Boeing Field in Seattle, WA, includes a tower-mounted sensor suite. The FTB is fitted with a sensor wing above and behind the cockpit, which accommodates the F-22's full-size wing-mounted antennas in their proper orientation. Internally, it features a complete CIP bank, an F-22 cockpit -- both the AIL and FTB support pilot-in-the-loop tests -- and multiple engineering workstations. The FTB has worked with Navy aircraft out of NAS Whidbey Island, WA, and with Air National Guard F-16s based at Albuquerque, NM.

The goal is to make the testing as realistic and repeatable as possible at each stage and, thereby, to minimize surprises at each succeeding stage. "The problem with integration is fault isolation," says Bender. "To do that, we need repeatability, combined with data gathering and reduction to get answers rapidly. If we can isolate faults on the FTB, it's a lot cheaper than doing the same on the F-22." The first elements of the engineering-and-manufacturing-development (EMD) sensor suite for the F-22 were installed on the 757 in 1998, and powered up for the first time in December of that year. These first tests used Block-i software, which comprised the basic operating system, navigation and some radar modes. Its primary goal was to unearth any basic problems "so that we wouldn't have to rewrite a lot of software later," says Bender. The Block-2 software, which integrates some EW and communication, navigation and identification (CNI) functions, has been operating on the FTB since October 1999, and will be loaded on to the fourth F-22 for its first flight.

Block 3.0 is the most crucial step forward, because it introduces sensor fusion among the radar, EW and CNI subsystems. A development version of Block 3.0, called Block 3S, has been flying on the FTB since April. Block 3S was added to the development program in early 1999, and includes sensor functions but not sensor fusion. "It is a risk-reduction tool," says Bender. "With the software controlling the sensors and fusion in the feedback loop, it's sometimes hard to unravel what happened. Did the sensor fail, or did it do what it did because we commanded it to do it?"

The real Block 3.0 is due to fly on the FTB in August before being loaded on Raptor 4004 in October or November. "It will be a challenge," says David Anderson of the F-22 Plans and Programs Division at Wright-Patterson AFB. "There is some risk there, depending on the availability of the aircraft and the software. The degree of risk depends on who you talk to." One area which is receiving some special attention, though, is throughput in the main computer. "We can't afford too much delay between the collection of the signal and the point where it is displayed to the pilot. We're overcoming that," says Anderson. But, he says, the team is confident that they will pass the milestone on schedule.

The schedule appears to be tight, with two to three months between the first flight of Block 3.0 on the FTB and its first flight aboard the F-22. "The current avionics schedule," notes a disapproving General Accounting Office (GAO) in its latest F-22 report, "shows Block 3...being completed five months before the completion dates the Air Force considered realistic in 1997." The first flight of 4004 slipped from February to May 2000 in the course of 1999, further delaying the flight testing of Block 2 aboard the fighter, and that date has since slipped to July. So far, however, the program has avoided disasters, and key changes (such as the implementation of Block 3S) have been implemented in time to avert problems.

UP NEXT: THE JSF

Both Lockheed Martin and Boeing are closely involved with the integration of the F-22 avionics, so it is not surprising that the proposed offensive avionics system for both JSF candidates takes the F-22 as a baseline. Sensor fusion, including the ability to detect, identify and locate pop-up threats quickly and accurately enough to attack them, is basic to the JSF. Both teams plan to fuse data on large-format displays and to use AESA radars in an LPI mode.

In many ways, JSF's goals are more advanced than those of the F-22. They include the fusion of synthetic aperture radar (SAR) and electro-optical systems in both the offensive and defensive modes. The JSF system is also intended to cost and weigh less than the F-22 hardware and to make extensive use of commercial, off-the-shelf (COTS) technology.

The JSF is planned to have five basic sets of sensors which, as on the F-22, will be entirely integrated into the central processor. Two of these form the Multi-Function Integrated Radio-Frequency System (MIRFS). The MIRFS/Multifunction Forward Looking Array (MFA) is the functional equivalent of the APG-77 radar and is being developed, under a separate competition, by Raytheon and Northrop Grumman; neither company is specifically teamed with either of the prime contractors on this part of the JSF program.

The MIRFS/Electronic Warfare System (EWS) is the all-around passive element of the RE system. The MIRFS/EWS will use its own dedicated antennas and the MFA. Sanders is the MIRFS/EWS supplier to both teams, basing its work on its experience with low-observable (LO) apertures for the F-22. Two sensor packages make up the EO system. The forward-looking BO targeting system (EOTS) is an infrared (IR) system to locate and help identify targets. The objective is to fuse JR and SAR imagery to detect and identify targets automatically with the minimum emission level. The EOTS will also function as a long-range IR search-and-track (IRST) system to detect airborne targets and as an EO system for airborne target identification.

The Distributed Aperture Infrared System (DAIRS) comprises a set of staring focal-plane-array (FPA) sensors covering a complete sphere around the aircraft and will combine three functions: it will feed a video signal to the pilot's binocular, day-night helmet-mounted display (HMD); will act as a missile-warning system, and will serve as an IRST to detect airborne threats.

The DAIRS and EOTS are the subject of a parallel competition, like the MIRFS/MFA. Northrop Grumman and Lockheed Martin Missiles and Fire Control form one team, with Northrop Grumman being responsible for the DAIRS and Lockheed Martin taking the lead on the EOTS. Boeing is presumably working with Raytheon. Both teams are using FTBs in the current demonstration and validation stage of the JSF program. Boeing began testing the JSF's integrated avionics on its 737-based Avionics Flying Laboratory (AEL) in December 1999 and plans a total of 50 missions. Lockheed Martin is using the BAG One-Eleven, which has served as an FTB for many Westinghouse and Northrop Grumman radars.

Although the teams have common suppliers in some areas (e.g., Sanders is the contractor for the MIRFS/EWS in both cases), there are detail differences. For example, Lockheed Martin has chosen Litton Advanced Systems to team with Sanders on the EWS, providing its unique expertise in electronic-support-measures (ESM) technology. In particular, Litton is applying its long-baseline interferometry processing to the Lockheed Martin JSF, providing the aircraft with twice the receiver capability of the ICAP-III Prowler to the Lockheed Martin JSF at half the size, weight and cost. BAB Systems is also a member of the team.

The EW and sensor systems proposed for the JSF would not be affordable using today's technology. One of the most costly aspects of the F-22 system is the need to provide separate antennas for all wavebands and aspects and to make those apertures compatible with stealth. F-22 antennas are installed in cavities lined with radar-absorbent material and covered with specially formulated materials which allow the signals of interest to pass through, while absorbing hostile signals. On the JSF, the goal is to reduce the cost and complexity of the antenna systems by making the antennas simpler and using a single antenna or aperture for many tasks.

Although Boeing and Lockheed Martin have demonstrated some key JSF functions on their test-bed aircraft, it is worth remembering that the F-22's avionics functions were demonstrated on the same level during the demonstration and validation phase of the ATF program in 1989-90. The GAO has said that several unspecified aspects of the JSF program are still not ready for EMD, and it is more than likely that the very sophisticated, yet low-cost technology proposed for the aircraft is among them.

Copy...They're sponges. I feel sorry for the avoinics techs. They must be pulling their hair out on a regular basis. A friend of mine owned a late model VW Beetle. To fix a problem with the instrument stack, they had to replace the radio.

I wonder how often the hardware will be updated on the F-22. There's going to be much more powerful computers and components in the future, with less weight, and this could lead to better overall performance in the identification of enemy A/C. The weight savings help too, as the F-22 is pretty heavy (not too much but it could be better). It probably flies and fights better than anything out there today, imagine 1,000 pounds lighter and with better computers

Wow, dude, that must be an awesome thing to be working on. I'm in college studying to be a computer engineer right now, and this year I signed up for AFROTC; I want to be an F-22 pilot and I'm hoping I can practice my computer programming skills as well once I get to the platform. Do you think they'll let pilots review the FCL and the overall sofware that goes into the A/C, or is that too secret still?

Pilots fly the jet, nothing else. They don't want people doing two jobs at once unless you are a test pilot. Even then, you have limited input and no chance to actually write software. That's not to say that you wouldn't have influence over those that do. Let me know if there is anything you need on your road to wings. With the current situation, you're going to need all the help you can get.

By the way, the Raptor community isn't all that great. You're always under the microscope, the pilots came from the Eagle community (they eat their young), and you are never going to be allowed to go to a merge. You might think about changing your mind and trying for the Viper/Lightning II community instead. We're cooler and we get to do more stuff.

SnakeHandlr- That's about the stupidest post of all time on here. You're basing those gross assumptions on how much time spent in the Raptor community? Zero?

For starters, there are other guys other than Eagle Drivers in the Raptor. For another, most of the senior guys have been in the community long enough that their previous platform has very little bearing on how they fly day-to-day now. Finally, not every thing that a Viper line dawg hears about the Eagle community is true anyway...shocking, I'm sure, but a lot of that line of BS is from bitter Viper pilots who just got their butts waxed by the F-15s.

Raptors go to merges just plenty...more so than the Eagle or the Viper, in fact. From what I've seen, they tend to arrive at the merge in a lot more advantageous position, simply because nobody has seen them up until that point. The majority of merges I've been in vs. Raptors ended up with their starting from an offensive advantage, after a late pickup by my element as they swung our six....not what I'd call a lot of fun for us. In at least half of those cases, we were already dead before we'd finished 90 degrees of defensive break.

I'd say the Raptors are a lot more willing to go to the merge.

Tinito - Keep your eyes on the prize. Fly what YOU want to fly. There's a ton of BULLS#!T out there about every platform, from Raptors, to Heavies, to White Jets. You'll have to sort through a lot of that on the ground. When you do get a chance to talk to the guys with the been-there, done-that, T-shirts, try to focus on the facts of their job day to day. Learn to filter out the obvious braggartry (and their will be some), and stick to the facts. Also, it's pretty lame to take what one guy says about another airframe as gospel. Typically, the younger the pilot, the more he'll slag off on the other jets with absolutely no idea what he's talking about. Senior majors and above tend to have seen more of the big picture, and have a much better idea of what each jet is capable of. They'll also be more likely to recommend somebody from other communities that'd be good for you to talk to.

Blu4
When you guys fly with Raptors are you using ACMI pods with recording capabilities? If so do you guys merge your mission on replay or do you just see your side of the fight?
I work at a Viper squadron so I'm curious if the ACMI system is used with those guys.

Blu4, let me guess, you're an Eagle driver or just a Raptor wannabe that didn't make the cut. It's okay, not everyone makes the right decisions in life. If you work really hard you can recover from this one too. Just because you weren't good enough doesn't mean you can't be part of the fight when they send you to the Predators. Apparently, you're lack of attention to detail is your downfall. The community of a jet has nothing to do with the flying part. The community has to do with the pilots and culture when they aren't flying, because lets face it, we don't fly nearly as much as we used to in the B-Course. I've hung out with pilots of all kinds from numerous countries. IN MY EXPERIENCE I've never met an Eagle pilot that struck me as "cool." With the few exceptions to prove the rule, they seem to me to be more self-centered, heartless and cruel to everyone around them. They are more stuck up and "holier-than-thou" because of the airframe they fly and their false sense of superiority. I even had a Raptor pilot correct me on the pronunciation of the jet's name. He actually stood their and expected me to pronounce it "Rap-tor" whereas I had pronounced it "Rap-ter" due to my accent. The jet doesn't even have an unofficial nickname (ie. Viper or Lawn Dart for the F-16) and already the pilots get their feathers ruffled when someone "mispronounces" their baby's name. Please, I left high school too long ago and I suggest they do the same. To this day, those that were there with me get a good laugh out of that guys superiority complex. Also, I spent some time with a former Viper driver and current Raptor pilot. He flat out told me that while he enjoys the flying, he dislikes the community and longs for the Viper lifestyle again. The more we talked, the more he confirmed by suspicions and agreed with my observations.

Furthermore, I could care less how a pilot acts in his jet because I'm not in it. I fly my jet the way I want to and you fly yours as you desire. Your statement is correct that some of the senior folks are not former Eagle drivers. Each one of the more senior pilots (patches by the way) have brought with them valuable knowledge and skills from their former weapons system required to make the Raptor the best at what it was designed for. The Eagle pilots specifically are masters of the air-to-air arena. The Viper has adopted many things from the Eagles in the way we now do air-to-air because we are willing to learn better techniques from those that know better. But in all of the former Eagle drivers who have come through Luke for Viper conversion, I have yet to meet one who looked at our techniques and tactics for air-to-ground with the same respect. One case that comes to mind regarding basic handling concerns not raising the gear immediately after a touch-and-go. Everything that is taught here for a month+ of academics and sims and in the TR phase is to not do that. But there now sits a centerline tank that has been half-ground down and two very luck guys that are still here because that event could have gone either way very easily.

What you also failed to mention is that Gen. Mosley has decried that no one outside of the Eagle community will be allowed to move to the Raptors anymore. But on the plus side, he has given us the increased chance of wonderful opportunities such as staff jobs, ALO tours and lets not forget TAMI21. But I'm glad he has protected at least some of the fighter pilots from the rapidly shrinking Air Force. It's nice to know that when someone from a community gets to a position of power that he'll remember those that he flew with and protect them and mold them into leaders of the future. I just hope that if I get the chance to lead that my actions will be as courageous.

In addition, just because someone is willing to go to the merge doesn't mean they will be allowed to. Honestly, if you were in charge, which would you rather risk, 120 million dollars or two older jets that don't owe the Air Force anything anymore and are getting close to retirement anyway. I have specific tactics in mind but that is a discussion for the vault.

Your Eagle attitude really shows in your posts. You don't take criticism very well and are horrified when people speak out based on THEIR OWN OBSERVATIONS. I grew up wanting to fly for the Navy, then I met enough of them and decided to go Air Force. I joined the Air Force wanting to fly the Raptor and the Eagles. Then I met enough of them and went with the Viper. Our opinions are created, changed and molded every day of our lives based on our experiences. Each of us is entitled to our opinion and I certianly hope Tinito speaks with enough of all of us before he forms one of his own.

Finally, if you are going to attack me personally, you better bring it a lot stronger than that brother. I feel like I'm back in high school and the playground bully is throwing a hissy fit because I looked at his girl the wrong way. I feel like I'm battling with an unarmed man.

Hey guys, easy. I can't speak from experience because I have none, but from what I hear and have seen, Dozer is an interesting person, seems cool, and he was an Eagle driver before going to the Raptor. Granted thats only one case, but it proves that not everyone is the same. I do agree that Gen. Mosely shouldn't have done that (restrict access to the Raptor only to former Eagle drivers), but then again, his thinking was somewhat rational because as far as I've read and heard, they're the masters in the Air to Air arena and the Raptor's suppossed to be an air superiority fighter. Although now they want to make the Raptor a bomber too...
I'm only just starting to know the Air Force and how it works, and hopefully in the time I take to finish my degree I'll be able to make a more informed decision as to where I want to go. Right now I just want to be a FIGHTER pilot regardless of which, because that's going to be hard as heck in itself and although I'm pretty good academically and I'm ok in fitness, my height is killing me. I'm only about 5'5 and a pilot candidate from my Det. told me that if youre too short you pass out quicker and that that could restrict the platforms I'm allowed to fly. I don't care if I have to consume hoards of salt and Red Bull to keep my blood pressure high and not pass out, but the ppl in charge aren't going to see it that way. And I'm afraid they just won't even let me fly fighters at all.

elp
I agree things went south quick. I operate the ACMI display systems, some may call it replay, for A/A ACMI engagements. I understand what is going on with a number of jet types because we work with all kinds.
I have never seen a 22 debriefed with other groups. I can understand why but I do get the feeling it may be very boring after a while just going up and killing everyone then come home. You would think the pilots edge would be lost over time if all they have to do is shoot kill shoot kill with no chance to really engage.
I would like to hear from some pilots and see what their thoughts are.